Development of ternary polymeric films based on cassava starch, pea flour and green banana flour for food packaging.

The development of alternative materials to replace plastics used in food packaging is an important approach to reducing environmental pollution and minimizing harmful impacts on ecosystems. In this study, biopolymeric films were formulated using cassava starch (Manihot esculenta Crantz), pea flour (Pisum sativum) and green banana flour (Musa sp.) to obtain a material for application in food packaging. The influence of a plasticizer on the optical and physicochemical properties of the films was analyzed and the synergy between higher concentrations of starch and plasticizer resulted in films with low opacity. In addition, the morphology, thermal, mechanical and barrier properties were examined. The film with the best formulation (p < 0.05) contained 12 g cassava starch, 3.6 g pea flour and 30 % glycerol (the maximum levels of the experiment). This film presented average values of thickness, moisture, solubility, opacity, maximum strength (F), maximum tensile stress (σ), elongation at break (ε) and elasticity (E) of 0.47 mm, 19.95 %, 87.45 %, 20.93 %, 9.30 N, 1.75 MPa, 30.10 % and 5.93 %, respectively. This research demonstrates the potential application of films obtained by combining starches from different sources. The sustainable production of environmentally-friendly packaging provides an alternative to fossil-based plastics, which have well-documented adverse effects on the environment.

Colorimetric detection of Pseudomonas aeruginosa by aptamer-functionalized gold nanoparticles.

Novel rapid methodologies for the detection of bacteria have been recently investigated and applied. In hospital environments, infections by pathogens are very common and can cause serious health problems. Pseudomonas aeruginosa is one of the most common bacteria, which can grow in hospital equipment such as catheters and respirators. Even at low concentrations, it can cause severe infections as it is resistant to antibiotics and other treatments. Based on this subject's relevance, this work aimed to develop a colorimetric biosensor using aptamer-functionalized gold nanoparticles for identifying P. aeruginosa. The detection mechanism is based on the color change of gold nanoparticles (AuNPs) from red to blue-purple through NaCl induction after bacteria incubation and aptamer-target binding. First, AuNPs were synthesized and characterized. The influence of aptamer and sodium chloride concentration on the agglomeration of AuNPs was investigated. Optimization of aptamer concentration and salt addition were performed. The best condition for detection was 5 µM aptamers and 200 mM of NaCl. In this case, P. aeruginosa was detected after 5 h for concentrations from 108 to 105 CFU mL-1, being 105 and 104 CFU mL-1 the detection limit for color change by the naked eye and UV-Vis spectrometry, respectively. In addition, other bacteria such as E. coli, S. typhimurium, and Enterobacteriaceae bacterium were also detected with color changing from red to gray. Finally, it was confirmed that the salt incubation time can be 2 h, and that the ideal aptamer concentration is 5 µM. Thus, the colorimetric analysis can be a simple and fast detection method for P. aeruginosa in the range of 108 to 105 CFU mL-1 to the naked eye. KEY POINTS: • A new method for rapid detection of Pseudomonas aeruginosa • Aptamers conjugated with gold nanoparticles allow pathogen detection by colorimetry • No need for previous surface modification of nanoparticles.

An overview and future prospects on aptamers for food safety.

INTRODUCTION: Many bacteria are responsible for infections in humans and plants, being found in vegetables, water, and medical devices. Most bacterial detection methods are time-consuming and take days to give the result. Aptamers are a promising alternative for a quick and reliable measurement technique to detect bacteria present in food products. Selected aptamers are DNA or RNA oligonucleotides that can bind with bacteria or other molecules with affinity and specificity for the target cells by the SELEX or cell-SELEX technique. This method is based on some rounds to remove the non-ligand oligonucleotides, leaving the aptamers specific to bind to the selected bacteria. Compared with conventional methodologies, the detection approach using aptamers is a rapid, low-cost form of analysis. OBJECTIVE: This review summarizes obtention methods and applications of aptamers in the food industry and biotechnology. Besides, different techniques with aptamers are presented, which enable more effective target detection. CONCLUSION: Applications of aptamers as biosensors, or the association of aptamers with nanomaterials, may be employed in analyses by colorimetric, fluorescence, or electrical devices. Additionally, more efficient ways of sample preparation are presented, which can support food safety to provide human health, with a low-cost method for contaminant detection. Key points • Aptamers are promising for detecting contaminants outbreaks. • Studies are needed to identify aptamers for different targets.